On Water: Metal-Free Synthesis of Highly Functionalized Benzothiazolylidene from ortho-Haloanilines

An environmentally benign, transition-metal-free organic base promoted one-pot cascade synthesis of highly functionalized benzo[d]thiazol-2(3H)-ylidene benzamide in the presence of water was accomplished by three-component reaction of ortho-iodoanilines, acrylates, and aroyl isothiocyanates. The protocol involves the in situ generation of thiourea intermediate followed by triethylamine induced intramolecular SN _Ar displacement reaction and subsequent Michael addition onto acrylate leads to the formation of benzo[d]thiazol-2(3H)-ylidene benzamide. Benzo[b]thiazole is also generated in good yields using amidation and intramolecular aromatic nucleophilic substitution chemistry. The control experiments support the proposed mechanistic pathway. Further X-ray crystallographic studies confirmed the assigned structures of the fused benzamide.